Magnesium oxide has numerous applcations in both agricultural and industrial fields. In the agricultural area, particularly, magnesium oxide is useful as an animal feed additive to raise magnesium blood serum levels, which prevents outbreaks of hypomagnesemia in cattle, and in fertilizers as a vital source of plant nutrient magnesium. In industry, magnesium oxide is useful as a boiler feed additive and is one of the primary reactant materials in many chemical process reactions, such as acid neutralization, cation replacement, and hydration reactions.
For many of these uses and applications, it would be advantageous to provide a high concentration aqueous magnesium oxide suspension to facilitate handling and ease of incorporation into a resultant product or reaction, or for use as a direct application material as in the case, for example, of a boiler feed additive, or as a boiler and air heater neutralization agent. However, prior art slurries or suspensions of magnesium oxide which use MgO having the surface area described by this invention at high concentrations exhibit excessive hydration of MgO to Mg(OH).sub.2, and resultant unacceptably high viscosity values for normal pumping and transport.
For example, prior art animal feed supplements commonly contain MgO with sources of nitrogen, phosphorous, and sugars. The insoluble magnesium oxide, however, frequently settles and/or causes formation of an immobile gel-like mixture, particularly at concentrations above about six percent. Various attempts have been made to achieve suspension stabilization of MgO containing feed supplements. Thus, in U.S. Pat. No. 4,219,572, Jackman et al. teach the presence of xanthan gum to stabilize liquid feed supplements containing a maximum of 6 percent MgO. The xanthan gum is said to provide suspension stabilization. As will be exemplified hereinafter, however, the MgO content may not be raised significantly above 6 percent without particularly deleterious effects upon the viscosity of the suspension. This is believed due to the fact that Jackman et al. do not employ a hydration inhibiting agent, such as is used in the present invention, to prevent hydration of the MgO to Mg(OH).sub.2.
In Mickus et al., U.S. Pat. No. 4,382,966, an animal feed suspension is taught wherein hydrated xanthan gum stabilizes the suspension by increasing the viscosity of the liquid supplements and forming a thixotropic gel. Lignin liquor may be added as a source of carbohydrate or sugar nutrient, and MgO may be added as an insoluble mineral nutrient. The goal of Mickus et al. is to achieve a high viscosity gel, directly opposite the goal of the present invention.
Falcione et al., in U.S. Pat. No. 4,230,610, teach the use of polyacrylates as a dispersant to reduce suspension viscosity and permit utilization of 41.6 percent MgO in a pigment dispersion.
Sawhill, U.S. Pat. No. 4,267,196, teaches an animal feed supplement containing sufficient ammonium orthophosphate or sulfate to form a gel, to which a dispersing agent such as gelatinized starch or clay is added to stabilize the insoluble solid nutrient. Lignin sulfonate may be utilized as a source of sugar or carbohydrate nutrient.
The prior art, accordingly, frequently seeks to achieve a gel state, and fails to disclose a concentrated, stable, hydration resistant suspension of from about 10 to 15 percent up to 50 percent MgO wherein suspension stability is improved by the presence of a suspension aid, and hydration of the MgO is prevented by the presence of an anti-hydration agent.